State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing, 210023, China; School of the Environment, Nanjing University, Nanjing, 210023, China.
Research Center for Eco-Environmental Engineering, Dongguan University of Technology, Dongguan, 523808, China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin, 150090, China.
Environ Res. 2023 Dec 15;239(Pt 1):117317. doi: 10.1016/j.envres.2023.117317. Epub 2023 Oct 6.
The emergence of anaerobic ammonium oxidation (anammox) coupled to iron reduction (named Feammox) refreshes the microbial pathways for nitrogen (N) loss. However, the ecological role of Feammox, compared with conventional denitrification and anammox, in microbial N attenuation in ecosystems remains unclear. Here, the specific contribution of Feammox to N loss and the underlying microbiome interactive characteristics in a riparian ecosystem were investigated through N isotope tracing and molecular analysis. Feammox was highlighted in the riparian interface soils and maximally contributed 14.2% of N loss. Denitrification remained the dominant contributor to N loss (68.0%-95.3%), followed by anammox (5.7%-19.1%) and Feammox (0-14.2%). The rates of Feammox and anammox significantly decreased in rhizosphere soils (0.15 ± 0.08 μg N g d for Feammox, 0.80 ± 0.39 μg N g d for anammox) compared with those in non-rhizosphere soils; however, the activities of denitrification remarkably increased in the rhizosphere (13.17 ± 3.71 μg N g d ). In rhizosphere soils, the competition between bioavailable organic matter (e.g., amino acids and carbohydrates) and ammonium for electron acceptor [i.e., Fe(III)] was the vital inducement for restricted Feammox, while the nitrite consumption boosted by heterotrophic denitrifiers was responsible for weakened anammox. The functional gene of autotrophic Acidimicrobiaceae bacterium A6, instead of heterotrophic Geobacteraceae spp., was significantly positively correlated with Feammox activity. Rare iron-reducing bacteria showed higher node degrees in the non-rhizosphere network than in the rhizosphere network. A syntrophic relationship was found between iron-reducing bacteria (e.g., Anaeromyxobacter, Geobacter) and iron-oxidizing bacteria (e.g., Sideroxydans) in the non-rhizosphere network and facilitated the Feammox pathway. This study provides an in-depth exploration of microbial driven N loss in a riparian ecosystem and introduces new insights into riparian management practices toward high-efficient N pollution alleviation.
厌氧氨氧化（anammox）与铁还原（称为 Feammox）的出现刷新了氮（N）损失的微生物途径。然而，与传统反硝化和 anammox 相比，Feammox 在生态系统中微生物氮衰减中的生态作用仍不清楚。在这里，通过氮同位素示踪和分子分析，研究了河岸生态系统中 Feammox 对 N 损失的特定贡献及其潜在的微生物相互作用特征。Feammox 在河岸界面土壤中很突出，最大贡献了 14.2%的 N 损失。反硝化仍然是 N 损失的主要贡献者（68.0%-95.3%），其次是 anammox（5.7%-19.1%）和 Feammox（0-14.2%）。与非根际土壤相比，根际土壤中 Feammox（0.15±0.08μgN g d ）和 anammox（0.80±0.39μgN g d ）的活性显著降低，而根际土壤中的反硝化活性显著增加（13.17±3.71μgN g d ）。在根际土壤中，生物可利用有机物质（如氨基酸和碳水化合物）和铵争夺电子受体[即 Fe(III)]的竞争是限制 Feammox 的重要诱因，而异养反硝化菌促进的亚硝酸盐消耗则是 anammox 减弱的原因。自养 Acidimicrobiaceae 细菌 A6 的功能基因，而不是异养 Geobacteraceae 菌，与 Feammox 活性呈显著正相关。在非根际网络中，稀有铁还原菌的节点度高于根际网络。在非根际网络中发现了铁还原菌（如 Anaeromyxobacter、Geobacter）和铁氧化菌（如 Sideroxydans）之间的共生关系，并促进了 Feammox 途径。本研究深入探讨了河岸生态系统中微生物驱动的 N 损失，并为河岸管理实践提供了新的见解，以实现高效的 N 污染缓解。
